1. Field of the Invention
The present invention relates to a centrifugal separator for separating particles from gas, comprising a separator chamber that comprises an upper portion delimited horizontally by walls and a lower portion having a downwardly decreasing horizontal cross section, the separator having means for defining therein a vertical gas vortex that comprise an inlet for gas to be dedusted formed in the upper portion of the chamber, an outlet for dedusted gas formed in said upper portion, and an outlet for separated particles formed in the lower portion of the chamber, said walls of the upper portion comprising at least a first, a second and a third substantially vertical planar walls, located one next to the other in the direction of flow of said gas vortex and defining three substantially vertical planar inner faces of said upper portion, said inlet for gas to be dedusted being formed in the vicinity of a first corner defined between said first and second walls, the inner faces of the first and second walls being substantially perpendicular and the inner faces of the second and third walls being substantially perpendicular.
The invention more specifically relates to a centrifugal separator for a circulating fluidized bed reactor device comprising a reactor chamber, a centrifugal separator and a back pass for heat recovery, the reactor device comprising means for introducing a fluidizing gas into the reactor chamber and for maintaining a fluidized bed of particles in said chamber.
2. Discussion of Related Art
In general, a reactor device is a boiler device where fuel particles (to which sorbent particles are suitably added for sulfur capture) are burnt in the reactor chamber, also named furnace or combustion chamber, and where heat generated is recover in the back pass, also named pass boiler, so as to produce energy (e.g. for driving electricity production turbines).
In such a reactor device, the gas to be dedusted—that contains particles—is transferred from the reactor chamber into the separator where the gas is dedusted. The separated particles are discharged from the separator and can be re-introduced, directly or indirectly, into the reactor chamber, also named combustion chamber. The dedusted gas is transferred from the separator into the back pass where heat of the gas is recovered by heat recovery areas located in the back pass.
The centrifugal separator being applied to a circulating fluidized bed reactor, this separator has to endure very high temperatures, the mixture of gas and particles entering the separator having a temperature of about 850° C., and the particles have an abrasive effect on the separator walls. The particles loading can be up to 20 kg/m3.
Therefore, it is necessary for these walls to have a strong structure that can resist high temperatures and abrasion.
In conventional separators, the separator chamber has a cylindrical shape with a circular cross section.
Such a shape offers a good separation capacity since it corresponds to the outer envelop of the vortex flow created in the chamber so that counter effects such as turbulences that could affect the separation efficiency are substantially avoided.
However, the cylindrical walls of such conventional separators are expensive to manufacture. This drawback is even more disadvantageous when, as explained above, the walls must be heat and abrasion resistant.
A separator having the upper portion of its chamber provided with planar walls is disclosed in EP-B-0 730 910. This separator has the cross section of its interior gas space defined by these planar walls in the shape of a polygon such as a rectangle or a square.
Such a separator is easier to manufacture and to assemble than the above described conventional ones.
However, an interior gas space having the shape of a polygon such as a rectangle or a square as shown in EP-B-0 730 910 offers quite a poor separation efficiency because the vortex flow generated therein cannot follow such a shape.
A solution for improving the separation efficiency may consist in providing several separators operating in parallel or in series. However, this solution is expensive and cumbersome.